Telephone-transmitter.



' PATENTED IUNE19, 1906.

W. WLDEAN.

TELEPHONE TRANSMITTER APPLICATION FILED EBB-T13, 1904.

Q SHEETS SHEET 1.

PATENTED JUNE 19, 1906,

2 SHEETS-SHEET 2.

I I W. W. DEAN TELEPHONE TRANSMITTER. APPLIOATIONVIEILED SEPT. 13, 1904.

THE NORRIS PETERS cm, wnsmuaruu; n, 6.

To all whom it 'may concern:

UNITE STATES,

PATENT 4; oFFro I LIAivI w. 'DEAN,C0F ELYRIA. onro, asslenoaro THE DEAN-anaemic! conrANY, OEE YRIA, OHIO, A CORPORATION ononrog ELE HoNE-rRANswuTTER;

Ila 823,768.

Be it known that I, WILLIAM W. DEAN, a citizen of the United States, residing at Elyria, in the county of Lorain and State of Ohio, have invented certain new and useful Improvements in Telephone-Transmitters, of which the following is 'a specification, reference being had therein to the accompanying drawings.

My invention relates to telephone-transmitters, "and more particularly to microphones inwhichgranular or finely-divided material, such as powdered carbon," is used as the resistance-varyin medium.

It has for its object t e production of an instrument ofthis class in which the parts shall be easy to assemble and adjustwithout any sacrifice of accuracy or exactnessand which shall be highly sensitive and efiicient when assembled and adjusted.

Thehighest type of granular-transmitter known in the art today is that'havinga sep-- arateresistance-chamber or button containing the electrodes and the granular material supported ,in proximity to the diaphragm, which is usually directly connected to one of the electrodes, while the other is rigidlyfixed, being attached to the frame of the instrument by means of a bridge or its equivalent. Thistype has been developed in-many forms and is widelyused commercially.- In spite vof this it is subject to cer-' tain drawbacks and defects inherent in the general design which prevent the attainment of full efficienoy. I'have discovered some of these defects and. in the design presented herewith haveremoved-them, with the result that my improved transmitter is not only of very high efficiency in individual in stances, as well'as easy to assembleand adjust, but its high efficiency and the adjust ments are uniform in all instruments of the t e. i I v i ne defect inherent in the transmitters heretofore used is the attachment of the diaphragm to the frontelectrode through-a cen-v tral 'and'very small portion of its superficial area. While the reatest amplitude of vibrationl theoretica 1y exists at this point, there is never' a sufficient area of connection to communicate positively a considerable amount of vibrant force. I remedy this by making a contact'connection between the Ielectrode-backand thediaphragm of sub- Specification of, Letters Patent.

Application filed September 13, 1904-- Serial No. 224,299-

stantially thev area of the electrode. An-

other defect is in the positive connections of In case of a very small va-. riation in drilling or assembling or in the punch that producesthe central opening in both electrodes.

the diaphragm the parts will not aline perfectly, and as the button is assembled sepa;

rately, with its two .stems presumably per.- fectly alined, there is a final slight distortion of the auxiliary diaphragm which creates a normal compression strain on one side of the.

chamber and the diaphragm and a tension strain on the other. 'The result is a drop in the individual instrument and lack of uni- Another defect is the formity in'the type. fixed character of the ordinary containing- P'atented June 19,19oe. I

cup, which permits the ranules therein to ack orto be packed. t is a well-known act that in thebest solid-back transmittersa packed condition of the carbonmaybe produced by placing the lips. to the mouthpiece and exhausting the air from in front of the diaphragm. The latter buckles forward, the. carbon drops into amass, and when the diaphragm through its own resilience goes back into normal position the carbon is compressed into almost solidity. It is impossible to purposely pack. my instrument and practically impossible to pack it through continue'd use, as 1 cause the containing-cup to move with the diaphragm, but do not fasten it thereto. Any forced movement of the dia phragm leaves the cup .behind, therefore, while ordinary packing is prevented by the constantagitation of the mass of granules. Another defect is in the lack of proper ten-. sion of the diaphragm. In a free. diaphragm suppbrted but not confined l-at the edges 1 I there is a certain dead zone ,in its travel, a-

' .certainspace extending either side of the central plane where the molecules of the metal are under practically no strain, or what strains there may be on opposite sides are balanced, and therefore nullified As the diaphragm swings one way a compression strain'is exerted on the inside and .a'tension on the outsideskin, its resilience depending upon this phenomenon. there is no resilience. The diaphragm V is dead, and the travel through that space, twice for each vibration, is equivalent to lost motion, so far as activity is concerned. This is partly overcome by the well-known dam- IOO In the dead space per-springs) but these are'not symmetric-5.

' Other defects might be pointed out; but these -panying drawings, in which ally placed, and their use is entirely without anyunderstandingof the principle I have discovered. I remedy this defect by putting the center of the diaphragm under a strain symmetrical at all times and useful in a secondary function of maintaining contact between the electrode-cup and the diaphragm.

are many of the apparent, and the method of overcoming them will also be a parent fronr my detailed. descri )tion. One fiiature of my transmitter should be mentioned here, however." By having no positive connection to the diaphragm from the cup or front electrode I have self-centering parts which cannot get out of alinement. Hence adjustments are uniform. Slight inequalities in the thickness of diaphragms are also taken up by the springs in adjusting, and the instrument is capable of a very fine adjustment, with high efliciency and great consequent sensitiveness.

My invention is illustrated in the accom- Figure l'is a sectional view of a granular transmitterembodying my improvements. Fig; 2 is a similar view of a modified form thereof, showing a preferred arrangement of the contact-springs and connections; and Flg. 3 1s a detail view of the bridge and springs shown 1n Fig. 2. a

In Fig. 1., A is a circular front plate, usually a casting, centrally apertured and screwthreaded to receive the mouthpiece A. This is preferably of hard rubber and is provided with the perforated septum c, adapted to protect the diaphragm of the instrument. The plate A upon its rear side is provided with an annular face a to receive the diaphragml), and in front of thediaphragm it is slightly recessed, as at a, to form a soundcha-mber. Around the peripher *of the plate I provide the rcarwardly-cxten ing flange a? and the surrounding bead a Extending from side to side and secured at opposite sides to the flange a is the bridge B, to which the resistance-button is connected. Extending about and inclosing the bridge and the working parts of the instrument is the shell A which takes "over and is secured to the flange e and abuts against the bead a thereby producing a neat finish. This shell has its central portion flattened, as shown, and provided with suitable apertures, so that it may be secured to the end of a hollow supporting-arm the conductors from which may pass into the shell and be secured to the respective circuit-terminals of. the instrument. Between the bridge B and the diaphragm D lie the working parts of the transmitter. These consist of the front and back electrodes E and E, inclosed in a rigid cup or casing C, which rests against the diaphragm. The

front electrode E is secured directly to the inner circular wall of the cup, While the rear 1 electrode E is carried upon a stem a, secured in the stud e, whlch 1n turn is rigidly held 1n the bridge. For the purpose of securing this stud firmly and in proper alinement the bridge is provided with a raised boss I), which may be integral therewith, but is shown as a rial not readily affected by h at and of an elastic nature. This is in the shape of a perforated disk slipped upon the stem c and firmly clamped between the electrode-plate E and the flat head of the stud r. The disk extends out around the electrode and overlies the peripheral flange c, formed on the cup C, being clamped thereto by means of a metal ring f and suitable screws or rivets. In Fig. l I have shown the flange and ring riveted together, and in Fig. 2 l have shown the ring threaded and screwed on the flange. The cup C rests with its bottom against the diaphragm I), being maintained in intimate contact therewith by means of springs S S, secured to and extending out from the flange a and having their inner ends respectively raised upon opposite sides of the ring f. I usually insulate these springs from the flange (1.", using them as a part of the circuit for the instrument for making electrical connection with the cup, and thereby one of the electrodes, and I may increase or decrease their tension bychanging somewhat their degree of curvature. They are preferably made of rather stiff spring metal, such as German silver, and I prefer tomake the cup C and the ring f of aluminium, so that little is to be feared from corrosion. In assembling this instrument the diaphragm is insulated by the soft-rubber band (1, which is sprung around its periphery and is held in place by the usual side springs. separate damper-springs commonly used with this type of transmitter I find-I do not need, the springs S performing their function perfectly. In fact, the damping action of the springs S being symmetrical and communicated to the diaphragm over a suitable central area is much superior to that of the ordinary springs, and from this springs a part of the superiority of my instrument. After the diaphragm is in place the cup C, held against it by the springs S and the bridge B, secured to its flange, the correct normal relative positions of the parts are determined by moving the stud e in the boss 6, and the adjustment (Not shown inFig. 1.) The' iszthen rendered permanent by setting up the screw 6.

a transmitter is sufficiently apparent from the will aflect the cup 0 or its contents, for the illustration and description. The cup 0 is not sup ort'ed upon the vdiaphragm, nor is it positivey connected" thereto, yet the springs S maintain a sufficiently intimate contact and a heavy enough pressureto insure most excellent transmlssion of the vibratory motions of the diaphragm to the cup and its movable electrode E. It will be observed thatthe parts are self-centering, that the carbon granules in the cup 0 are constantly agitated to prevent their packing, and that no abnormal or violent movements of the diaphragm reason that themovements of the cup are limited by the mica disk F, as well as by its own inertia, the latter, however, being small.

' In Fig. 2 I have shown a similar construction, withthe exception that all circuit connections are insulated from the bridge or the shell of the transmitter. This is a point of some importance in 'a transmitter to be used in common battery systems, as it is now common to emlplo potential differences of forty to fifty vo ts between the central-oflice terminals. With such voltages and considerable self induction in the circuits it is quite possible to obtain annoying shocks in the use of a telephoneas, for instance,-b grasping the transmitter-shell with one and and touchingthe switch-hook with the other if both are uninsulated as regards the main circuit. By the-" cons'tructionsho'wn in Figs. 2

' and 3, however, I do away with all danger of shocks. In these figures the Workingparts are all the same as described in connection with Fig. 1. Instead of having the springs S extend from the side flange, however, I make these springs in one integral U-shaped' iece 7 and secure them beneath the'brid'ge bushed screw-bolt and nut s s, the construc-' tion being such that a strong-mechanical connection is produced, as wellas a thoroughlyinsulated binding-post. The central boss I) v is in this case carried upon a plate 12 separated ir'omthe bridge but attached thereto by the bushed screws 1) and 6 Between the plate and the bridge and extending also beneath the insulated ost s is a sheet of insulating material, suc as hard rubber, 12 The central boss 7) lies in anopening b in the bridge large enough to give a clearance all around the boss, so that any accidental contact in assembling is impossible. The circuit of the instrument as thus constructed is to the screw s, double spring S, screw-ring f, flange 0, on C, electrode E, through the granularcar on to electrode E, through the stem e and the stud e to the boss I) and plate b and out. All'the parts included 1n thls circuit are insulated, so that the line has absolutely no connectlon with instrument,

The operation of this form of the shell of the Having thus described my invention, it

will be apparent how I have attained my obects. overcomeby I tween the diaphragm and the vibrating cup. The second ,and third objections are obviby disconnecting the cup from the diaphragm entirely. The 'fourth defect is removed by supplying the tension-springs S, which, do

The first defect mentioned'aboveis thelarge .area of contact be-,

. ated-by making the parts self-centering and away with the dead-point vibration of the H diaphragm. Y My transmitter has many advantages not hereln specifically mentioned and which become apparent upon considering the method of construction. I

I .am aware that many changes mabe made in matters of'detail without sacri cing these advantages ,as long as the principal features of the invention are attained, and it is therefore to be'understood that all such changes and modifications are contemplated byme as fully within the scope and purview o my invention.

Having thus described my invention,what

'1. Ina telephone-transmitter, a vibrating diaphragm, an independently-supported cup having an electrode, springs pressing said cup against the diaphragm, a second electrode independently and rigidly fixed with respect to the first, and ranular conducting material between the eIectrodes in the cup.

2. In a telephone-transmitter, a vibrating diaphragm, a containingcu separately supported but vibrating with t e dlaphragm, an

electrode seated in said cup, a secondelecdiaphragm, a containing-cup independently supported but vibrating with the dlaphragm, one electrode seated in said cu a second electrode fixed wth respect to t e first, an

auxiliary dia hragm peripherally secured to the edge oft e cup and connecting the samewith the fixed electrode, together with granular conducting material in the cuo and between the electrodes, substantially as described.

9 v I claim, and desire to secure by Letters Patent, 1s'

' 5. In a telephone-transmitter, a vibrating I diaphragm, an indep randomly-supported contalni-ng-cup s ring-pressed against the dia-. phragm', an e ectrode seated in the cup, a

second electrode fixed wth respect to the first, an auxiliary diaphragm peripherally secured to the on and centrally secured to the fixed electro e, together with granular I 5 conducting material in the cup and between the electrodes, substantially as described.

6. In a telephone transmitter, a diaphragm, a pair of electrodes, and a contain- I ing-cup therefor, one electrode vibrating with 10 the diaphragm and the other fixed in a suitable support, a contact-spring secured to but insulated from said support and pressing against the conducting parts connected with the movable electrode, together with means to insulate the fixed electrode from the sup- I5 port, whereby circuit may be made throu h the electrodes without passing through t e su porting parts, substantially as described. testimony whereof I afiix my signature in presence of two witnesses.

WILLIAM W. DEAN. Witnesses:

RAY H. MANSON, I. A. BEYLAND. 

